How to use a member function (delegate) as a function pointer

[Daniel Murphy]

"Peter Federighi" <pfederighi at yahoo.com> wrote in message 
news:ial8hq$2137$1 at digitalmars.com...
> Is there a way to do it without removing handler() from the class?  When I 
> try
> compiling, I get: Error: cannot implicitly convert expression 
> (&this.handler)
> of type void delegate(int signal) to void C function(int).

Yes, but it requires some nasty code.

(Not tested on anything except windows)
http://yebblies.com/thunk.d

(Also not tested)

import yebblies.thunk.d;
import std.c.linux.linux;
import std.stdio;
class FOO
    {
    this()
        {
        th = thunk!"C"(&handler);
        sa.sa_handler = th.ptr;
        sigemptyset(&sa.sa_mask);
        sa.sa_flags = SA_RESTART;
        sigaction(SIGALRM, &sa, null);
        }

    ~this()
        {
        sa.sa_handler = SIG_DFL;
        sigemptyset(&sa.sa_mask);
        sa.sa_flags = SA_RESTART;
        sigaction(SIGALRM, &sa, null);
        }

    private:
    sigaction_t sa;
    typeof(thunk!"C"(&handler)) th;

    void handler(int signal)
        {
        writeln("Got an alarm signal.");
        }
    }

It basically gets around the restriction by writing some code into memory 
that passes the delegate params in unused registers.  I don't even know if 
the page allocation code works on anything except windows.

Daniel